Dr Pepper

So this marinade is great. Got it from a chef I know
4 lbs of skirt steak ( flat iron, or flank)
16 oz of Dr Pepper, 4 cloves of garlic and two cinnamon sticks. In a zip lock bag over nite
Dry it off in the fridge for two hours
Salt pepper garlic powder
3-4 mins a side at high heat
Little red in side cut diagonal with the grain
Delish

I have done something similar with Coke. Check your instructions. Any of those cut " with " the grain will very tough and stringy. I am thinking you meant " across " the grain. The long muscle fibers will be cut short and be more tender...JJ